Winter automobile or light truck tire including sipes

ABSTRACT

A radial pneumatic light truck or automobile tire 10 having a tread 12 which has a plurality of traction elements 20,30 aligned in rows and separated by wide circumferential grooves 24 and a plurality of narrow laterally inclined grooves 26,36. Each traction element 20,30 is divided into at least three zigzag portions by a plurality of wavy patterned sipes 28,38. The wavy pattern of sipes 28 within the central rows of traction elements 20 are laterally extending. The wavy pattern sipes 38 in the shoulder rows are circumferentially extending. The preferred tire 10 has the laterally extending narrow grooves 26 being wavy and along with the wavy sipes 28 of a traction element 20 having peak amplitudes (A) aligned along a linear path (L) inclined at an angle θ, relative to the equatorial plane (EP). Axially adjacent central rows of traction elements 20 are oppositely inclined.

This application is a continuation in part of application Ser. No.08/570,951 filed Dec. 12, 1995.

BACKGROUND OF THE INVENTION

The present invention is related to a tread for a vehicle tire. Inparticular, the present invention relates to improvements to the treadof an automobile or light truck tire which is particularly well adaptedfor winter travel under snowy and icy conditions.

Winter or snow tires have historically been designed with treads havinglarge traction lugs that were widely spaced yielding a very low roadcontacting surface within the tires normally loaded footprint. Theseopen tread patterns are excellent in deep snow. However, due to thelarge lugs and open tread pattern these tires are notorious forgenerating substantial noise and vibration when used on rain soaked ordry paved roads. The tread wear rate is rapid and therefore these tiresare considered for use only during the snowy winter months. These tiresare not particularly well suited for icy road conditions.

Many driving enthusiasts have chosen to use all season type treads.These tread patterns employ wide transverse grooves and circumferentialgrooves defining discrete tread elements. The tread patterns aresubstantially more closed than a pure snow tire yet are sufficientlyopen to provide good snow traction and overall acceptable tread wear andnoise performance. The primary advantage to the all season tread is thatthe tires can be used year round. A fundamental disadvantage is that thetires are not as good as snow tires in severe winter conditions and canbe particularly poor in icy or freezing rain conditions.

Under these icy road conditions metal studs or cleats are considered theoptimal traction solution. Unfortunately in many localities the use ofsuch traction aides is prohibited because of the tremendous road damagethat can result and in those areas where these types of studded tiresare permitted the legal use is generally limited in duration.

The use of treads having a high density of sipes within the tractionelements has been determined to provide a good improvement to both snowand ice traction performance. Such heavily bladed tires can exhibit goodwinter ice traction performance by providing an increase number of treadedges to provide forward traction.

One particularly significant prior art winter tire exhibiting theemployment of multiple bladed sipes combined with a plurality ofcircumferential and transverse grooves is disclosed in U.S. Pat. No.5,198,047. This tire, commonly known as the Goodyear Ultra Grip 4 Tire,has a directional tread pattern. That is the tread had a preferreddirection of travel adapted to yield superior traction in one direction.This directional tread pattern was symmetrical about the equatorialplane of the tire. The sipes were arranged angularly similar within eachtread half and oppositely tread half to tread half to further enhancethe directional traction performance by insuring a first portion of thesipe always enters and leaves the footprint prior to the second ortrailing portion. The tire has demonstrated excellent directionaltraction and reasonable noise properties. The tire tread of the presentinvention although useable in these directional type tread patters isespecially well adapted to provide excellent all direction travel thusmaking the tread nondirectional, which is a most beneficial feature in awinter tire.

The present invention employs narrow transverse grooves and a novelarrangement of wavy sipes so as to achieve a winter tire havingexcellent snow and ice traction properties in all directions of travelincluding forward, backward and during turning or cornering maneuvers.The tread pattern also exhibits very low noise and has interlockingtraction elements that greatly reduces the Residual Self-Aligning Torque(RSAT) that is commonly exhibited in such tires.

SUMMARY OF THE INVENTION

A radial pneumatic light truck or automobile tire 10 having a tread 12having low noise generation and particularly well suited for snow andice traction is described.

The tread, when incorporated in the tire 10, has an axis of rotation(A/R), a pair of lateral edges 14,16, a tread width (TW) defined as theaxial distance between lateral edges 14,16, and an equatorial plane (EP)perpendicular to the axis of rotation (A/R) and spaced equivalent fromthe lateral edges 14,16.

The tread 12 has a tread base 18, a plurality of traction elements 20,30extending radially outwardly from the tread base 18, a plurality ofcircumferentially continuous wide grooves 24, a plurality of narrowlaterally extending grooves 26,36 and a plurality of sipes 28,38.

The circumferentially continuous wide grooves 24 extend radially fromthe tread base 18 and divides the plurality of traction elements 20,30into a plurality of rows of traction elements. One shoulder row isadjacent each lateral edge 14,16 and two or more central rows oftraction elements 20 are deposed between the shoulder rows.

The tread has a plurality of narrow laterally inclined grooves 20,30 onesuch groove 26,36 separating each circumferentially adjacent tractionelement 20,30. In the preferred embodiment the narrow grooves 26separating the traction elements 20 of the central rows are of a wavypattern having at least three equal peak amplitudes (A). The wavypatterned sipes 28 extend across and divide each traction element 20within the central rows into at least two preferably three zigzagportions. The wavy patterned sipes 28 preferably have two or moresubstantially equal peak amplitudes (A). In the preferred embodiment onepeak amplitude (A) of each of the sipes 28 and each of the narrowgrooves 26 of each traction element 20 within a central row is alignedin a linear path (L), the linear path (L) is inclined relative to theequatorial plane (EP) at an angle ζ, θ being less than 45°. Axiallyadjacent central rows have the linear path (L) oppositely inclinedrelative to the linear path (L) of an axially adjacent central row oftraction elements 20.

The wavy sipes 38 of the shoulder row traction elements 30 arecircumferentially extending and divide each traction element 30 into atleast two, preferably three circumferentially extending zigzag portions.

The combination of wavy sipes 28,38 and grooves 24,26,38 as arrangedacross the tread 12 provide excellent snow and ice traction. Theinterlocking tread elements 20,30 are highly flexible with lengthy bladeedge surfaces for snow and ice traction in all directions of travel. Theshoulder siping 38 creates enhanced traction of the tread 12 duringcornering maneuvers. This greatly helps the driver to maintain controlof the vehicle in the circumstance most likely to induce a slippage ofthe tread 12 on the icy road surface. Prior art tire designersheretofore have made elongated lateral extending lugs for high lateralstiffness. The present invention goes against that conventional wisdomby dividing the shoulder traction element 30 into at least threeportions increasing the lateral flexibility and providingcircumferential blade edges to provide icy condition cornering tractionas will be discussed in the detailed description of the invention.

DEFINITIONS

"Aspect Ratio" means the ratio of a tire's section height to its sectionwidth.

"Asymmetric tread" means a tread that has a tread pattern notsymmetrical about the centerplane or equatorial plane (EP) of the tire.

"Axial" and "axially" means lines or directions that are parallel to theaxis of rotation of the tire. "Block Element" means a tread elementdefined by a circumferential groove or shoulder and a pair of lateralextending grooves.

"Circumferential" means lines or directions extending along theperimeter of the surface of the annular tread perpendicular to the axialdirection.

"Compensated tread width" means the tread width multiplied by the aspectratio.

"Equatorial Plane (EP)" means the plane perpendicular to the tire's axisof rotation and passing through the center of its tread.

"Footprint" means the contact patch or area of contact of the tire treadwith a flat surface at zero speed and under normal load and pressure.

"Groove" means an elongated void area in a tread that may extendcircumferentially or laterally about the tread in a straight, curved, orzigzag manner. Circumferentially and laterally extending groovessometimes have common portions. The "groove width" is equal to the treadsurface area occupied by a groove or groove portion, the width of whichis in question, divided by the length of such groove or groove portion;thus, the groove width is its average width over its length. Grooves maybe of varying depths in a tire. The depth of a groove may vary aroundthe circumference of the tread, or the depth of one groove may beconstant but vary from the depth of another groove in the tire. If suchnarrow or wide grooves are of substantially reduced depth as compared towide circumferential grooves which they interconnect, they are regardedas forming "tire bars" tending to maintain a rib-like character in thetread region involved.

"Inboard side" means the side of the tire nearest the vehicle when thetire is mounted on a wheel and the wheel is mounted on the vehicle.

"Lateral" means an axial direction.

"Net contact area" means the total area of ground contacting elementsbetween defined boundary edges divided by the gross area between theboundary edges as measured around the entire circumference of the tread.

"Net-to-gross ratio" means the total area of ground contacting treadelements between the lateral edges around the entire circumference ofthe tread divided by the gross area of the entire tread between thelateral edges.

"Non-directional tread" means a tread that has no preferred direction offorward travel and is not required to be positioned on a vehicle in aspecific wheel position or positions to ensure that the tread pattern isaligned with the preferred direction of travel. Conversely, adirectional tread pattern has a preferred direction of travel requiringspecific wheel positioning.

"Outboard side" means the side of the tire farthest away from thevehicle when the tire is mounted on a wheel and the wheel is mounted onthe vehicle.

"Radial" and "radially" means directions radially toward or away fromthe axis of rotation of the tire.

"Rib" means a circumferentially extending strip of rubber of the treadwhich is defined by at least one circumferential groove and either asecond such groove or a lateral edge, the strip being laterallyundivided by full-depth grooves.

"Sipe" means small slots molded into the tread elements of the tire thatsubdivide the tread surface and improve traction.

"Tread element" or "traction element" means a rib or a block element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the preferred embodiment tire accordingto the present invention.

FIG. 2 is a plan view of the tire of FIG. 1.

FIG. 3 is a view of a portion of the tread pattern of the tire shown inFIG. 2.

FIGS. 4A through 4E illustrate cross sectional views of the treadelements, grooves and sipes taken from FIG. 3.

FIGS. 5, 6 and 7 are views of a portion of alternative embodiment tiresaccording to the present invention.

FIG. 8 is a cross sectional view of a tire 10 according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, a perspective view and a plan view of theradial ply pneumatic light truck or automobile tire 10 according to thepreferred embodiment of the invention is shown. The tire 10 has a tread12. The tread 12 when incorporated in the tire 10 has an axis ofrotation (AR), a pair of lateral edges 14,16, a tread width (TW) definedas the axial distance between lateral edges 14,16 and an equatorialplane (EP). The equatorial plane (EP) is a plane perpendicular to theaxis of rotation and spaced equidistant from the lateral edges 14,16.

The tread has a tread base 18, a plurality of traction elements 20,30extending radially outwardly from the tread base 18, a plurality ofcircumferentially continuous wide grooves 24, a plurality of narrowlaterally extending grooves 26,36 separating circumferentially adjacenttraction elements 20,30 and a plurality of laterally extending wavypatterned sipes 28 and a plurality of circumferentially extending wavypatterned sipes 38.

The circumferentially continuous wide grooves 24 divide the plurality oftraction elements 20,30 into a plurality of rows of traction elements.One shoulder row of traction elements 30 is adjacent each lateral edge14,16 and two or more central rows of traction elements 20 is deposedbetween the shoulder rows. In the illustrated preferred embodiment thetread is divided into five rows of traction elements, two shoulder rowsand three central rows, by four circumferentially continuous widegrooves 24.

As shown in FIG. 3, the narrow grooves 26 separating the tractionelements 20 of the central rows are of a wavy pattern having at leastthree substantially equal peak amplitudes (A).

The laterally extending wavy patterned sipes extend across and divideeach traction element 20 within the central rows into at least threezigzag portions. The wavy patterned sipes 28 have two or moresubstantially equal peak amplitudes (A).

The preferred embodiment tread has one peak amplitude (A) of each of thesipes 28 and each of the narrow grooves 26 of each traction element 20within a central row aligned in a linear path (L). The linear path (L)is inclined relative to the equatorial plane at an angle θ, θ being lessthan 45°. The traction elements 20 of axially adjacent central rows havethe linear path (L) oppositely inclined relative to the linear path (L)of an axially adjacent central row of traction elements. As shown inFIG. 3 linear path (L) has an orientation θ in the central row nearestthe lateral edge 14 which varied due to the pitching of the treadelements 20. Orientation θ is 20° for the largest pitch P_(L), 24° forthe medium pitch P_(M) and 28° for the smallest pitch P_(S). The centralrow of traction elements 20 at the equatorial plane has the orientationθ, being respectively -20°, -24°, -28°, for the large, medium, and smallpitches respectively. The central row nearest the lateral edge 16 hasthe orientation θ, being respectively 20°, 24°, 28°, for the large,medium, and small pitches, respectively. These angularly inclinedalignments of the tread elements 20 at the location of the peakamplitudes in combination with the interlocking fitment of adjacenttread elements 20 within a row can be arranged to contribute to thereduction of residual self aligning torque commonly referred to as RSAT.The tire engineer can selectively incline the path (L) to create atorque or bending moment in each row of traction elements relative tothe equatorial plane. Depending on the tire carcass and numerous otherfactors the linear path (L) can be selected to generate an offsettingtorque.

As can be seen from the FIGS. 1 through 3 the traction elements 20 ofthe central rows have substantially straight circumferentially extendingends 21 adjacent the wide circumferential groove 24. Thecircumferentially adjacent elements 20 within each row have the axialends 21 axially offset relative to the other adjacent traction elements20 in repeating sequence. The amount of axial offset is preferably atleast approximately a length of one half the peak amplitude (A) of thewavy pattern groove or sipe. The axial offset of the ends 21 createsadded traction surfaces in the snow.

Referring to FIGS. 1 through 3 the tread 12 has shoulder rows withtraction elements 30 adjacent at least one, preferably both lateraledges 14,16. The elements 30 within the shoulder rows are separated by anarrow laterally extending inclined groove 36. These traction elementshave a circumferential extent or length approximately twice that of thecircumferential length of the traction elements 20 of the central rows.As illustrated each traction element 30 has an end 31 having twoparallel straight portions 31A,31B adjacent the circumferential groove24. Both straight portions are inclined relative to the equatorial planeat an angle θ₂, θ₂ being less than 45° and opposite in inclination ofthe linear path (L) of the axially adjacent central row. Thisarrangement of the ends 31A,31B is complimentary to the reduction ofRSAT generation and likewise can be increased in inclination to generatea somewhat compensating torque within the row. It must be appreciatedthat the further the row is away from the equatorial plane the lessinclination is needed to induce a compensating moment or torque.

An interesting and very novel feature shown in the shoulder row oftraction elements 30 is the wavy patterned sipes 38. Two or more suchcircumferentially extending wavy pattern sipes 38 extend across thetraction element 30 intersecting the narrow lateral grooves 36 dividingthe traction element 30 into three portions 30A,30B,30C. The threeportions 30A,30B, and 30C have interlocking adjoining zigzag endsdefined by the wavy sipes 38.

Conventional wisdom has directed the tire engineer to axially elongateshoulder elements and to buttress such features to create lateralstiffness when the tire is subjected to cornering maneuvers. The tire 10of the present invention deliberately divides the element 30 into threedistinct but cooperating portions which have sufficient lateralstiffness enhanced by a shoulder extension 40 integral to the portion30A. The shoulder extension 40 connects the element 30 to the uppershoulder region of the tire 10. Under turning maneuvers the threeportions 30A,30B,30C are flexed into the adjoining portion each portionproviding lateral resistance and contributing to the stiffness of theelement 30. Most importantly the circumferential sipes 38 provideelongated biting edges to grip the iced over road. The tire engineer inthe past has provided forward and backward traction for ice but once thesteer tire are turned relative to the direction of travel the effectivetraction is greatly diminished. The present invention recognizes thatthe driver has to turn the vehicle when driving and has accounted forthis fact by adding the elongated wavy sipes 38 in the shoulder elements30.

A particularly beneficial feature of the wavy sipes 28,38 is the amountof peak amplitude A provided as shown in FIGS. 1-3. The peaks are formedwith an included angle approximating normal or perpendicular creatingalmost isosceles triangular features, the distance between peaks beingabout equal to the amplitude (A). The effective length of such sipe isalmost twice that of the overall length of the element 20,30. Thisgreatly increases the length of tread edges provided to grip the roadsurface. The sipes 28 of the center row are inclined primarilylaterally, however, due to the sharp zigzag and pronounced amplitude (A)about half of the edge length of any given sipe 28 is normal to thedirection of travel during turning maneuvers. The overall effect is amuch more controllable tire particularly on ice, regardless of thedirection of travel. The tire of the present invention has excellentstarting and stopping straight line traction while exhibiting farsuperior turning traction compared to tires of the prior art.

Referring to FIGS. 4A through 4E cross sections of portions of the tread12 are shown. These cross sections reflect the radial depth of the sipes28,38 and the narrow lateral grooves 26,36 relative to the tread base18. The radial depths of sipes generally are not greater than the depthof the main grooves usually somewhat less. Furthermore, the depth canvary across the sipe.

The present invention being a snow tire relies heavily on the edgescreated by the sipes for traction. For that reason the depth of thesipes are almost full depth except for that portion intersecting agroove 24,36.

FIG. 4A illustrates the sipe 28 of a center row traction element 20. Thedepth (d) is about 70% of the nonskid depth, the nonskid depth being thedepth of radially outer surface relative to the surface of the treadbase 18. At the intersection of the grooves 24 the depth (d₂) of thesipe is reduced to about 25% of the nonskid.

In FIG. 4B the narrow lateral groove 26 is shown having a radial depth(d) of 90% of the nonskid depth (dns) across the entire groove length.

In FIG. 4C the sipe 38 of the shoulder traction element has a depth (d)of 90% of the nonskid depth (dns) except at the center of the sipe 38where the depth (d₂) is only 50% of the nonskid and at the intersectionof the lateral grooves 36 a depth (d₃) of 25% of the nonskid occurs.

FIG. 4D the sipe 38 closest the lateral edges has a depth (d) of 70% ofthe nonskid except at the intersection of the grooves 36 where the depth(d₂) is only 25% of the nonskid.

FIG. 4E shows the depth of the narrow lateral groove 36 the depth (d)being 90% of the nonskid.

The above cross sectional views of the various components show theeffort to maximize the useful life of the tread in terms of tractionperformance while also maintaining the structural integrity of the treadelements 20,30. It is believed important that the two or morecircumferentially wavy sipes 38 of the shoulder elements 30 have radialdepths in the range of 50% to 100% of the radial height of the tractionelements 30 over a majority of the sipe length.

It is further believed preferable that the sipes 28,38 have a sawtoothconfiguration. Alternatively, the pattern can be somewhat sinusoidal tofacilitate fabrication of the blades which form the sipes.

FIG. 5 shows an alternative embodiment of the invention wherein thenarrow grooves 46 are of a wavy pattern similar to the narrow groove 26as opposed to being of the straight groove 36 shown in FIG. 1.

Alternatively as shown in FIG. 6 groove 56 can be formed as narrow as asipe having either the wavy or the straight line configuration. Thisalternative configuration can improve the noise dampening effect of thetread 12 and further tends to stiffen the shoulder row of elements 30 byeffectively making the shoulder into a rib-type construction.

A preferred tread 12 however is as shown in FIGS. 1-4E having superiortraction and excellent noise dampening achieved in part by reducing thenumber of narrow grooves 36 in each of the shoulder rows to about halfthe number employed in each of the central rows of elements 20. Also thegroove 36 being inclined somewhat circumferentially and opening into alarge noise diffusing outer portion 58 of the shoulder createsadditional sound deadening properties.

A more preferred alternative embodiment tread 12 of the invention isillustrated in FIG. 7. The lateral grooves 36 have been modified toinclude a first portion 72 and a second portion 74. The first portion 72intersects the circumferential groove 24 and has a first or leadinggroove wall 80 including a chamfer 81 and a trailing groove or secondgroove wall 82. The distance at the intersection of the groove 24 of thefirst and second groove walls 80,82 is about equal to the nominal groovewidth of the circumferential groove 24, the distance X₁, being about 9mm. the groove walls 80,82 narrow to a minimal distance as it extendsoutwardly toward the shoulder the minimum distance is about 3 mm or1/3χ₁. As the groove 36 extends outwardly from the minimal point 85 tothe noise diffusing portion 58 it widens in groove width to between 2/3to 100% χ₁, preferably about 75% of χ₁. This widening of the groove 36greatly enhances snow traction and has demonstrated an additional 8.5%improvement in curved aquaplaning performance of the tire of FIG. 7 whencompared to the tire of FIGS. 1-4B. This improvement is directlyattributable to the change in the groove 36 shape. As a furtherenhancement, a pair sipes 90 where added to each shoulder block element.The sipes 90 are laterally extending and further enhance ice tractionwhile increasing the circumferential flexibility of the tread shoulderblock portion 30A. This widening of the lateral groove still exhibitsacceptable noise properties because the narrowing and subsequentwidening of the groove coupled with the sipes 90 diffuse and dampen thenoise energy such that the tire remains remarkably quiet for itsintended application.

FIG. 8 is a cross sectional view of the tire 10 employing the noveltread 12 is shown. The tire 10 of the preferred embodiment has a carcassa pair of annular beads 45, a pair of radial plies 47, extending frombead 45 to bead 45 and wrapped at about each bead 45, a beltreinforcement 49 radially above the plies 47 and a pair of sidewalls 41,one sidewall 41 extending from each bead 45 to the tread 12. The treadis radially outward and adjacent the belt reinforcement 49. Thoseskilled in the art can appreciate that the number of plies 47 and belts49 employed can be any number including but not limited to a single plyor a single pair of belt reinforcements.

What is claimed is:
 1. A radial ply pneumatic light truck or automobiletire having a tread, the tread having an axis of rotation, a pair oflateral edges, a tread width (TW) defined as the axial distance betweenthe lateral edges, and an equatorial plane perpendicular to the axis ofrotation and spaced equidistant from the lateral edges, the treadcomprising:a tread base; a plurality of traction elements extendingradially outwardly from the tread base; a plurality of circumferentiallycontinuous wide grooves extending radially from the tread base anddividing the plurality of traction elements into a plurality of rows oftraction elements, one shoulder row being adjacent each lateral edge andtwo or more central rows of traction elements being disposed between theshoulder rows; a plurality of narrow laterally inclined groovesseparating each circumferentially adjacent traction element, the narrowgrooves separating the central rows of traction elements being of a wavypattern having at least three substantially equal peak amplitudes; aplurality of laterally extending wavy patterned sipes extending acrossand dividing each traction element within the central rows into at leastthree zigzag portions, the wavy patterned sipes having two or moresubstantially equal peak amplitudes, for each traction element within acentral row one peak amplitude of each of the sipes in the tractionelement and of each of the narrow grooves which define a respective edgeof the traction element being aligned in a linear path (L), the linearpath (L) being inclined relative to the equatorial plane at an angle θ,θ being less than 45°, the traction elements of one of the central rowshaving the linear path (L) oppositely inclined relative to theinclination of the linear path (L) of the traction elements of anaxially adjacent central row; and wherein at least one of the shoulderrows has traction elements having a circumferential length approximatelytwice that of the circumferential length of the traction elements of thecentral rows, each traction element of the shoulder rows having an endhaving two straight portions adjacent the circumferential groove, bothstraight portions being inclined relative to the equatorial plane at anangle θ₂, θ₂ being less than 45° and opposite in inclination of thelinear path (L) of the axially adjacent central row, the narrowlaterally inclined grooves separating the traction elements of theshoulder rows each having an axially inner end intersecting thecircumferential groove, the inner end defined by a first and a secondgroove wall, the first groove wall having a chamfer.
 2. The radialpneumatic light truck or automobile tire of claim 1 wherein eachtraction element of the central rows has substantially straightcircumferentially extending ends adjacent the circumferential grooves,wherein the circumferentially adjacent elements within each row have thecircumferentially extending ends axially offset relative to each other.3. The radial ply pneumatic light truck or automobile tire of claim 1wherein each traction element of the at least one shoulder row has twoor more circumferentially extending wavy pattern sipes extending acrossthe traction element intersecting the narrow lateral grooves anddividing the element into at least three portions.
 4. The radial plypneumatic light truck or automobile tire of claim 3 wherein the two ormore circumferentially extending wavy sipes have a radial depth in therange of 50% to 100% of the radial height of the shoulder row tractionelement over a majority of the sipes lengths.
 5. The pneumatic radialply light truck or automobile tire of claim 1 wherein the tread hasthree central rows of traction elements.
 6. The pneumatic radial lighttruck or automobile tire of claim 1 wherein the wavy pattern of thesipes is substantially a saw tooth configuration.
 7. The pneumaticradial light truck or automobile tire of claim 1 wherein the wavypattern of the sipes is substantially sinusoidal.
 8. The pneumaticradial light truck or automobile tire of claim 1 wherein a distance (d)between adjacent peak amplitudes of adjacent sipes within a tractionelement is less than or equal to an amplitudal distance (A) between theadjacent peaks of one of the adjacent sipes.
 9. The radial ply pneumaticlight truck and tire of claim 1 wherein a distance χ₁ between the firstand second groove wall at the intersection of the circumferential grooveis about equal to the width of the circumferential groove as measured atthe radially outer surface of the tread.
 10. The radial ply pneumaticlight truck or automobile tire of claim 9 wherein the lateral groovenarrows to a minimum width of less than 1/3χ₁ adjacent the chamfer andwidens thereafter as it extends axially outwardly to the shoulder to amaximum of 75% to 100% χ₁.
 11. A radial ply pneumatic light truck orautomobile tire having a tread having an axis of rotation, a pair oflateral edges, a tread width (TW) defined as the axial distance betweenthe lateral edges, and an equatorial plane perpendicular to the axis ofrotation and spaced equidistant from the lateral edges, the treadcomprising:a tread base; a plurality of traction elements extendingradially outwardly from the tread base; a plurality of circumferentiallycontinuous wide grooves extending radially from the tread base anddividing the plurality of traction elements into a plurality of rows oftraction elements, one shoulder row being adjacent each lateral edge andtwo or more central rows of traction elements being disposed between theshoulder rows; a plurality of narrow laterally inclined groovesseparating each circumferentially adjacent traction element; a pluralityof laterally extending sipes, at least two laterally extending sipesextending across and dividing each traction element within the centralrows into at least three portions; a plurality of circumferentiallyextending sipes, at least two circumferentially extending sipesextending across and dividing each traction element within at least oneshoulder row into at least three portions, andwherein the laterallyextending grooves and sipes of the central rows of traction elementshave a wavy pattern which divides each traction element within thecentral rows into at least three zigzag portions, the wavy patternedlaterally extending sipes and grooves of the central rows having two ormore substantially equal peak amplitudes, for each traction elementwithin a central row one peak amplitude of each of the sipes in thetraction element and of each of the narrow grooves which define arespective edge of the traction element being aligned in a linear path(L), the linear path (L) being inclined relative to the equatorial planeat an angle θ, θ being less than 45°, the traction elements of one ofthe central rows having the linear path (L) oppositely inclined relativeto the inclination of the linear path (L) of the traction elements of anaxially adjacent central row; and the traction elements in the shoulderrow includes a pair of lateral extending sipe adjacent the tread edge.12. The radial pneumatic light truck or automobile tire of claim 11wherein each traction element of the central rows has substantiallystraight circumferentially extending ends adjacent the circumferentialgrooves, wherein the circumferentially adjacent elements within each rowhave the circumferentially extending ends axially offset relative toeach other.
 13. The radial ply pneumatic light truck or automobile tireof claim 11 wherein at least one of the shoulder rows has tractionelements having a circumferential length approximately twice that of thecircumferential length of the traction elements of the central rows. 14.The radial ply pneumatic light truck or automobile tire of claim 11wherein the two or more circumferentially extending sipes have a radialdepth in the range of 50% to 100% of the radial height of the shoulderrow traction element over a majority of the sipes lengths.
 15. Thepneumatic radial ply light truck or automobile tire of claim 11 whereinthe tread has three central rows of traction elements.
 16. The pneumaticradial light truck or automobile tire of claim 11 wherein the pattern ofthe sipes is substantially a saw tooth configuration.
 17. The pneumaticradial light truck or automobile tire of claim 11 wherein the pattern ofthe sipes is substantially sinusoidal.
 18. The radial ply pneumaticlight truck or automobile tire of claim 11 wherein each traction elementof the shoulder rows has an end having two straight portions adjacentthe circumferential groove, both straight portions being inclinedrelative to the equatorial plane at an angle θ₂, θ₂ less than 45° andopposite in inclination of the linear path (L) of the axially adjacentcentral row.
 19. The pneumatic radial light truck or automobile tire ofclaim 11 wherein a distance (d) between adjacent peak amplitudes ofadjacent sipes within a traction element is less than or equal to anamplitudal distance (A) between the adjacent peaks of one of theadjacent sipes.